Erythrocyte Aggregation and Blood Viscosity is Similar in Homozygous Sickle Cell Disease Patients with and without Leg Ulcers.

Background There is no consensus regarding the role of red blood cell (RBC) aggregation in the pathogenesis of leg ulcers (LUs) in sickle cell disease (SCD). Objectives We sought to evaluate whether the cross-sectional determination of RBC aggregation and hematological indices were associated with the presence of LU in homozygous SCD. Methods Twenty-seven patients with LU and 23 with no history of ulceration were recruited into the study. A laser-assisted rotational red cell analyzer (LoRRca) was used in the determination of the aggregation index (AI), aggregation half-time ( t1/2 ), and the RBC aggregate strength (AMP). Hematological indices were determined using a CELL-DYN Ruby analyzer. Whole blood viscosity (WBV) and plasma viscosity (PV) were measured using a Vilastic bioprofiler. The data were presented as means ± standard deviation or median, interquartile range. Two-sample t -test was used to test for associations between the AIs, WBV, and PV in patients with and without LU. Statistical significance was taken as p < 0.05. All analyses were conducted using Stata/SE v . 12.1 (StataCorp, College Station, TX). Results The AI was comparable in the group with and without ulcers (68.6, 16.7 versus 67.7, 16.9; p = 0.74); t1/2 (1.7, 1.3 versus 1.8, 1.3; p = 0.71); AMP (18.8, 14.5 versus 19.1, 13.3; p = 0.84), WBV (3.8, 1.2 versus 3.8, 0.7; p = 0.77); and the PV (1.3, 0.08 versus 1.4, 0.1; p = 0.31) and were also not statistically different between the groups of participants. Conclusion RBC aggregation and aggregate strength are not associated with leg ulceration in SCD.

In vitro effects of co-incubation of blood with artemether/lumefantrine & vitamin C on the viscosity & elasticity of blood.

BACKGROUND & OBJECTIVES: The antimalarial combination drug artemether/lumefantrine has been shown to be effective against malaria parasite through its haemolytic action. This drug is sometimes co-administered with vitamin C in patients with malaria. Vitamin C is associated with antioxidant properties which would be expected to protect against haemolytic effects of this antimalarial drug. This study was designed to investigate in vitro effects of co-incubation of artemether/lumefantrine with vitamin C on the viscosity and elasticity of blood. METHODS: Blood was collected from 12 healthy female volunteers with normal haemoglobin genotype (HbAA). A Bioprofiler was used to measure the viscosity and elasticity of untreated blood samples (control) and samples exposed to artemether/lumefantrine (0.06/0.36 mg/ml) alone and with low or high dose vitamin C (equivalent to adult doses of 100 or 500 mg). RESULTS: artemether/lumefantrine significantly (p<0.05) reduced viscosity of blood from 4.72 ± 0.38 to 3.78 ± 0.17 mPa.s. Addition of vitamin C (500 mg) further reduced blood viscosity to 2.67 ± 0.05 mPa.s. The elasticity of blood was significantly (p<0.05) reduced from 0.33 ± 0.04 mPa.s to 0.24 ± 0.03 mPa.s by the antimalarial drug, and further reduced to 0.13 ± 0.02 mPa.s in the presence of vitamin C (500 mg). INTERPRETATION & CONCLUSIONS: Co-incubation of blood with vitamin C and antimalarial combination drug potentiates the haemolytic effects of the latter on reducing blood viscosity and elasticity in vitro. This may possibly have implications in relation to haemolysis in patients receiving vitamin C supplementation with artemether/lumefantrine during malaria therapy.

The in vitro effects of sulfadoxine/pyrimethamine and artemether/lumefantrine on the viscoelasticity of erythrocyte membrane of healthy females.

Fansidar® (sulfadoxine/pyrimethamine) and Coartem® (artemether/lumefantrine) are drugs that destroy malarial parasites and also produce free radicals which cause hemolysis of malaria-parasitized erythrocytes. This study investigated the effect of these drugs on the viscoelasticity of erythrocytes of ten healthy female subjects using the BioProfiler. The concentration for each of the two drugs were determined based on the therapeutic dose as normal, half the therapeutic dose as low and double the therapeutic dose as high. For Fansidar®, the concentrations were 0.15/0.01 mg/ml (low), 0.30/0.02 mg/ml (normal) and 0.60/0.04 mg/ml (high) based on the adult therapeutic dose of 1500/75 mg of sulfadoxine/pyrimethamine in the drug combination. For Coartem®, the concentrations were 0.03/0.19 mg/ml (low), 0.06/0.38 mg/ml (normal) and 0.12/0.76 mg/ml (high) based on the adult therapeutic dose of 320/1920 mg of artermether/lumefantrine in the drug combination. There was a statistically significant (p < 0.05) decrease in viscosity, elasticity and relaxation time with Coartem® at normal and high doses. Fansidar® also showed significant (p < 0.05) reductions in these parameters only in the high dose. This suggests that Coartem® generated significant free radicals at normal and high doses, with Fansidar® only in the high dose, resulting in increased hemolysis and ultimately reduced viscoelasticity.

Optimal haematocrit in subjects with normal haemoglobin genotype (HbAA), sickle cell trait (HbAS), and homozygous sickle cell disease (HbSS).

The determination of an optimal haematocrit (H0) has important clinical implications if such a level can be attained, and more importantly, maintained. This is defined as a haematocrit level, above or below which oxygen delivery is deleteriously affected. This study is designed to determine an optimal haematocrit in normal (AA), sickle cell trait (AS) and sickle cell disease (SS) subjects. Twenty-seven apparently healthy subjects having normal haemoglobin genotype, 24 with sickle cell trait and 42 with homozygous sickle cell disease were recruited into the study. Whole blood viscosity (WBV) was measured by a Wells Brookfield Cone and Plate Viscometer at a shear rate of 230 sec-1. Haematocrit was determined by an AC.Tron Coulter Counter. The optimal haematocrit was calculated as the inverse of a constant, K, which was derived from the haematocrit and viscosity data. Our findings showed that the H0 varied significantly among the 3 haemoglobin genotypes, in the order AA vs SS and AS vs SS. Additionally, the data indicated an increased H0 in subjects with sickle cell trait, suggesting a possible impairment in oxygen delivery in these individuals.

In vitro erythrocytic membrane effects of dibenzyl trisulfide, a secondary metabolite of Petiveria alliacea.

We investigated the in vitro effect of dibenzyl trisulfide (DTS), a secondary metabolite of Petiveria alliacea, on erythrocyte elasticity, relaxation time and membrane morphology. Blood samples from 8 volunteers with hemoglobin AA were exposed to 100, 200, 400, 800 and 1000 ng/ml of DTS respectively and the elasticity and relaxation time measured. There were statistically significant, dose-dependent increases in elasticity and relaxation times. The changes in membrane morphology observed also increased with increased concentration of DTS. This suggests that DTS interaction with membrane protein resulted in increased elasticity, relaxation time and deformation of the erythrocyte membrane.

Oxygen delivery index in homozygous sickle cell disease: steady and crisis states.

One of the common complications of sickle cell disease is the vaso-occlusive crisis or sickle cell crisis which could result in impaired oxygen delivery to the tissues. This study investigates the oxygen delivery index (ODI) in 38 patients with homozygous sickle cell anaemia. Thirty-three patients were in the steady state and five were experiencing crisis at the time of recruitment. Whole blood viscosity was measured with a Wells Brookfield viscometer at a shear rate of 230 sec(-1) and haematocrit was measured with an AC Tron Coulter Counter. The ODI, which is an indirect measure of the capacity of blood to deliver oxygen to tissues, was calculated as the ratio of haematocrit to whole blood viscosity values. There was no statistically significant difference in the ODI between the steady and crisis states, suggesting that tissue oxygenation is not the only factor involved in the sickle cell crisis.

Oxygen delivery index in subjects with normal haemoglobin (HbAA), sickle cell trait (HbAS) and homozygous sickle cell disease (HbSS).

Sickle cell disease is characterized by altered blood rheology due to a reduced haematocrit and a resulting lowered viscosity. Oxygen carriage, and consequently oxygen delivery, may be deleteriously affected if the haematocrit reduction is such as to limit oxygen uptake from the lungs and delivery to the tissues. The present study seeks to determine and compare the oxygen delivery index (ODI) in subjects with normal and abnormal haemoglobin genotypes. Thirty four apparently healthy subjects having normal haemoglobin genotype (AA), 27 with sickle cell trait (AS) and 50 with homozygous sickle cell disease (SS) were recruited into the study. Whole blood viscosity was measured at low and high shear rates of 23 s(-1) and 230 s(-1), respectively, using a Wells Brookfield Cone and Plate Viscometer. Haematocrit was determined using an AC.Tron Coulter Counter. The oxygen delivery index was calculated as the ratio of the haematocrit to whole blood viscosity. There was a statistically significant difference in the ODI in the SS group compared with both the AA and AS groups. There was no statistical significance in the ODI between the AA and AS groups. The ODI may be considered as a useful assessment of oxygen delivery in subjects with sickle cell disease.

Increased incidence of adverse perinatal outcome with low maternal blood viscosity in preeclampsia.

Hyperviscosity of the maternal blood has been reported to be associated with an increased incidence of adverse perinatal outcome in preeclampsia. We related the changes in maternal blood viscosity to perinatal outcome in 47 preeclamptic, nulliparous, black Jamaican women. A group of 49 non-preeclamptic, nulliparous, gestation-matched women acted as controls. Perinatal outcome was also compared between the women with high blood viscosity (> or = 5 mPa.s) and those with low blood viscosity (< 5 mPa.s) in both the preeclamptic and non-preeclamptic groups. Data was analysed by the comparison of two proportions, the chi-squared test, the Fisher's exact test and the Pearson's correlation method. The level of statistical significance was taken at p < 0.05. The incidence of adverse perinatal outcome was significantly (p < 0.001) higher in the preeclamptic women as compared with that of the non-preeclamptic controls. However, of interest, was the fact that within the preeclamptic group, the incidence of adverse perinatal outcome was significantly (p = 0.001, Fisher's exact test) higher in those with low blood viscosity as compared with those with high blood viscosity. These results suggest that low maternal blood viscosity may be related to increased incidence of adverse perinatal outcome in Jamaican women with preeclampsia.

Erythrocyte deformability and erythrocyte aggregation in preeclampsia.

One of the features of preeclampsia is impaired blood rheology due to altered erythrocyte aggregation and erythrocyte deformability. We investigated these two parameters which affect the viscosity of blood, along with serum and intraerythrocytic magnesium concentrations, immunoglobulin titres and fibrinogen concentration in 12 preeclamptic women. Eighteen (18) other non-preeclamptic, gestation-matched women acted as controls. Erythrocyte deformability, expressed as elongation index (EI), and erythrocyte aggregation expressed as aggregation half-time (t 1/2) were measured with the Laser-assisted Optical Rotational Cell Analyser (LORCA). Serum and intraerythrocytic magnesium concentrations were analysed by atomic absorption spectrometry, immunoglobulin titres by radial immunodiffusion and fibrinogen concentration by a clot weight technique. There was no statistically significant difference in these parameters between preeclamptics and controls suggesting that erythrocyte deformability and aggregation as well as serum and intraerythrocytic concentrations, fibrinogen levels and immunoglobulin titres are not altered in preeclampsia. Further investigations are required in severe preeclampsia and in preeclamptic women taking magnesium sulphate supplement.

Is there hyperviscosity in pre-eclampsia?

There are conflicting reports on blood viscosity and its determinants in pre-eclampsia. We investigated the presence of hyperviscosity and its determinants in 25 nulliparous, pre-eclamptic Jamaican women. An equal number of non-pre-eclamptic, gestation-matched women served as controls. There was no statistically significant difference in whole blood, plasma and serum viscosities, as well as in their determinants, namely, haematocrit, fibrinogen, IgM and IgG concentrations between the pre-eclamptic and control groups. This suggests that hyperviscosity is not a feature of pre-eclampsia in this Jamaican population.

Is there hyperviscosity in Pre-eclampsia?

There are conflicting reports on blood viscosity and its determinants in pre-eclampsia. We investigated the presence of hyperviscosity and its determinants in 24 nulliparous, pre-eclamptic Jamaican women. An equal number of non-pre-eclamptic, gestation-matched women served as controls. There was no statistically significant difference in whole blood, plasma and serum viscosities, as well as their determinants, namely, haematocrit, fibrinogen, IgM and IgG concentrations between the pre-eclamptic and control groups. This suggests that hyperviscosity is not a feature of pre-eclampsia in this Jamaican population.

Sickle cell trait: dual picture of blood films.

The picture of the blood films of subjects with the sickle cell trait is still controversial. While some authors report the presence of sickled cells in the blood films of these subjects, others disagree. This paper submits that sickled cells could be seen in the blood films of subjects with the sickled cell trait, especially in those resident in high altitude areas.

On the protective mechanism of the sickle cell trait (HbAS).

The sickle cell trait has been reported to offer some protection against anaemia in pregnancy. Some attribute this to the break up of the cells which release iron for the synthesis of haemoglobin. The hypothesis presented here is that the 'partial' protective mechanism of the sickle cell trait is due to increased erythropoietic activity.